Since September 11, 2001, the world has been hearing a lot about Islamic fundamentalism. Yet fundamentalism itself is a general term that applies to more than just an extreme part of the world of Islam. The term does not denote a separate religion at all, but is a particular way of looking at one's own religion.
The word fundamentalism goes back about one hundred years. At the time, it represented a reaction within the more conservative Protestant churches in America to the challenge that Darwinism, the theory of human evolution, seemed to present to traditional Christian belief. In response to what many sincere Christians believed was a threat to the Biblical story of creation—in which God creates the world and universe out of nothing—these more conservative groups adopted a dogma that required people to accept a particular interpretation of Scripture, including its literal infallibility. The movement was a defense against modernism, a defense against change that seemed to threaten the purity of their Christianity.
In similar fashion, Islamic fundamentalism has grown up at a time of immense change in the Islamic world—in countries that have changed very little for centuries. In many cities of the Middle Eastern crescent stretching from North Africa to Iran, a growing middle class has adopted Western dress, accepted Western ways, and so on. In other words, Western economic interests in the area, combined with an invasion of a foreign culture that usually accompanies an increase in trade and investment abroad, threatened the time-accepted norms of Islamic culture. The only way to preserve that culture and religion, in this view, was complete rejection of the culture and economic ways that came from the West. So, one can see how Islamic fundamentalism was also a reaction against threatening change.